Compression bone screws are used in operations in order to join together two fragments of a broken bone under compression. The compression assists the knitting of the two fragments.
Such a compression bone screw is known from U.S. Pat. No. 4,858,601. This is a double-threaded screw comprising three separate components. Two of these components each bear a thread with the same thread pitch and the same thread diameter. The two threaded components provided with a thread are each designed as a hollow-cylindrical sleeve.
The third component of the compression bone screw is a pin-shaped shank subdivided into two opposite shank halves along its axial extent and provided with a diameter enlargement at one of its two ends. The two sleeve-shaped threaded components are fitted onto the shank one after the other in such a way that the diameter enlargement of the shank acts as a stop for the two threaded components. After this, the threaded component fitted last onto the shank is connected in a rotationally fixed manner to the shank by soldering. The other of the two threaded components, in contrast, is freely rotatable about the shank as an axis of rotation.
Both the diameter enlargement of the shank and the threaded component rotatable with respect to the shank are each provided with a force-receiving structure in the form of a slot. The slots enable the separate application of a torque to the rotatable threaded component and also to the threaded component connected in a rotationally fixed manner to the shank.
To fasten the screw, two screwdrivers each with a different blade are used. The blade of the first of the two screwdrivers is designed to cooperate with the slot in the diameter enlargement of the shank, and the blade of the second of the two screwdrivers to cooperate simultaneously with the slot in the rotatable threaded component and also with the slot in the diameter enlargement of the shank. While the second screwdriver consequently permits the screwing-in of the bone screw as a whole, the first screwdriver enables a relative rotation between the two threaded components.
The object on which the invention is based is to specify a compression bone screw which is simple to produce. The further object on which the invention is based is to specify a screwdriver blade for such a compression bone screw.